Reciprocating floor slat conveyors typically involve a set of load-supporting slats that all move together in one direction, and then return, one-third at a time, in the other direction. Because the dynamic frictional surface contact area between slat surfaces and load is less during slat return, the load is inched along by the conveyor apparatus as the slats move back and forth. Floor slat reciprocation is usually always driven by hydraulics, with some variation in unloading speed, depending on different variables.
Reciprocating floor slat systems are often built into truck trailers that haul bulk materials like gravel, as an example. This type of design is used as an alternative to a dump truck (having a conventional hoist lift).
When reciprocating floor systems are used in a trailer, it is desirable that the trailer and reciprocating floor be left clean after an unloading operation. For this reason, several “cleanout” designs have been developed in the past. One cleanout design is described in U.S. Pat. No. 7,510,071, which describes a “plow” style cleanout apparatus. A more common type of cleanout apparatus is the flexible tarp system described in U.S. Pat. No. 6,974,296, issued to Simrin.
All of these cleanout systems involve a floor tarp portion, or something similar, that rides along the floor with the load. Usually, some of the load's material rests directly on the tarp, thus increasing the frictional forces between the tarp and the reciprocating floor slats underneath, so that the tarp sweeps the floor relatively clean by pulling a vertical barrier or headboard behind it as the trailer is unloaded. Either a portion of the tarp or other structure built aft of the tarp creates the cleanout surface that functions like a moving wall for preventing material from leaking forward as the cleanout apparatus moves aft during the unloading operation.
At the end of the unloading procedure, the tarp mostly exits and hangs over the end of the trailer before it is reeled back to the forward end of the trailer. One of the problems with this design is that the end of the tarp is sometimes buried in the pile of unloaded material sitting on the ground. The weight of the unloaded material sitting on the buried tarp stresses the tarp material and/or the tarp return mechanism when it is operated to pull the tarp free. Sometimes truck drivers will roll the truck forward to simply pull the tarp out of the load—which creates the same kind of problem.
A different problem associated with prior art systems is that they have a tendency to allow a certain amount of material to pass (or leak past) their lateral edges during the unloading process. Poor cleanout along the lateral edges of the cleanout system is more of a problem for loads like gravel or sand, as examples, because left-over material from one load may contaminate the next load involving a different kind of material. It is undesirable to have sand from one load mixed with asphalt in the next, as an illustrative example.
For the above reasons, there is a need to improve upon existing cleanout systems that are tailored for reciprocating floor assemblies.